For car manufacturers it is important to have a signature design for the light sources of the car. Often the light sources comprise a strip shaped light source with Light Emitting Diodes (LEDs) that follows curves in several dimensions, for example, in a first dimension that is defined by a corner of the car and in a second dimension that follows a portion of a partly circular circumference of a front light. Often car manufacturers have to order strip shaped lighting assemblies that are already manufactured in the required shape. There is a need to have a general elongated shaped lighting arrangement that can be bended by the car manufacturer into a specific shape as defined by the design of the light source of a specific car.
Today, in several lighting applications, flexible LED strips are used on which Light Emitting Diodes (LEDs) are provided. The known flexible LED strips use in general a flexible strip-shaped substrate on which power lines are provided to which the LEDs are locally coupled. There may be two power lines and all LEDs may be arranged parallel to each other. The flexible LED strip may also comprise one or more series arrangements of LEDs that are locally coupled in between two main power lines. Then several series arrangements of LEDs are arranged parallel to each other—then the flexible strip has locally tree electrical conductive tracks for transporting electrical energy. The term lead frame may be used for the flexible strip-shaped substrate. In general the term lead frame refers to the metal structure coupled to a semiconductor device that carries the signals and power from the semiconductor device to the outside world. In the context of Light Emitting Diodes (LEDs), the term lead frame refers to the arrangement to which the LEDs are coupled and which carries power and optional signals to the LEDs. Thus, with respect to the known flexible LED strips, the term lead frame refers to the flexible strip-shaped substrate with power lines and electrodes to which the LEDs may be coupled.
In general those flexible strips, which are based on the strip-shaped substrates, are only bendable in one dimension, namely in a direction perpendicular to a plane defined by the flexible strip if the strip is arranged flat—for example, the flexible strip-shaped substrate can be (spirally) coiled up. This flexibility is rather limited and there is a need for more flexible strip-shaped LED lead frames.
The published US patent application US2013/0188369A1 describes a LED 3d curved lead frame of an illumination device. In an embodiment, the 3d curved surface may comprises an elongated stack comprising alternating electrically conductive layers and dielectric layers. The elongated stack locally comprises island structures for receiving a LED and in between the island structures the width of the stack is thinner than at the island structures. In this context it is assumed that the length of the elongated stack is defined from one end of the elongated stack to another end and that the height is defined in a direction from a bottom layer towards a top layer. According to the document, such LED 3d curve lead frames can be bended up to a certain degree such that it can be arranged on a slightly curved surface of an illumination device.
The flexibility of the above discussed flexible LED strips and the LED 3d curved lead frame of the cited US application are limited because 3 conductive layers and 2 isolation layers are stacked or laminated on each other and the flexibility is, for example, not sufficient for the above discussed application in car light sources.